Due to increasing scarcity of fluid fossil fuels such as oil and natural gas, much attention is being directed towards converting carbonaceous material such as coal, oil shale, and solid waste to liquid and gaseous hydrocarbons by pyrolyzing the carbonaceous material. Pyrolysis can occur under nonoxidizing conditions in the presence of a particulate source of heat.
The particulate source of heat may be obtained by at least partially oxidizing a carbon containing solid residue resulting from the pyrolysis of the carbonaceous material. In order to maximize recovery of the heating value during the oxidation of the carbon containing solid residue, it is desirable to maximize the production of carbon dioxide and minimize the production of carbon monoxide. However, the kinetics and thermodynamic equilibrium of the oxidation of carbon favor increased production of carbon monoxide relative to carbon dioxide at temperatures greater than about 1200.degree. F and as the reaction time increases. Since pyrolysis of carbonaceous materials often is conducted at temperatures greater than 1200.degree. F and can approach temperatures as high as 2000.degree. F or higher, it is necessary to form a particulate source of heat having temperatures greater than 1200.degree. F. Thus production of carbon monoxide inevitably occurs in the oxidation step because of the high temperatures used and long residence times encountered in high capacity systems. The carbon monoxide formed represents a loss of thermal efficiency of the process.
Therefore, there is a need for a process for preparing a particulate source of heat for the pyrolysis of a carbonaceous material by the oxidization of a carbon containing solid residue of the carbonaceous material which maximizes production of carbon dioxide and minimizes production of carbon monoxide.